1. Field of the Invention
The present invention relates to an ignition device for propulsive charge of a ammunition round including the telescoped type having a casing that is generally cylindrical in shape in which a pyrotechnical composition and a device for igniting the composition are housed.
Generally, the propulsive charge of an ammunition round is ignited using an ignition device, usually called an igniter, which protrudes through the base of the round into the body of the propulsive charge.
2. Background Art
Patent FR-2 343 987 describes a traditional ignition tube intended for artillery ammunition including a cylindrical case housing a pyrotechnic charge and an ignition element therefor, for example, a fuse activated from the outside using a striking pin. The casing is extended via a tubular component which contains an ignition charge consisting of annular compressed blocks of black powder. The free end of the tubular component is closed with a combustible cap which is ejected and burnt by the gases of combustion from the charge. Radial openings are distributed along the length of the tubular component and are closed off with covers that are broken by the pressure from the gases. Thus, flames produced by the pyrotechnic charge may reach parts of the propulsive charge located near to the opening. Therefore, the longer the tubular component, the deeper the penetration into the charge, and the more likely it is that the ignition of this charge will take place under better conditions, in relation to optimum conditions correspond to a virtual instantaneous ignition of the propulsive charge.
In the case of telescoped ammunition, the projectile is arranged inside the casing or case containing the propulsive charge, rather than protruding therefrom. Thus, it is possible to define a shorter ammunition round which enables more compact weapons or weapons with higher rates of firing to be designed. In order to maintain the same ballistic performance of traditional ammunition, the casing of the ammunition is filled with the greatest amount possible of the propulsive charge, including an annular layer of charge disposed around the projectile.
When the projectile of the telescoped ammunition includes, for example, a sub-projectile that terminates usually in a tail section, the result is that the distance separating this tail section from the base of the ammunition is inadequate to house therein a traditional igniter which has the power appropriate for the mass of the charge to be ignited. Designs utilizing a smaller, less powerful igniter do not permit virtual instantaneous ignition of the charge.
Another design, as described in documents U.S. Pat. Nos. 4,907,510, 4,846,069, 4,782,758 and 4,858,533, consists of dividing the propulsive charge into two parts which are ignited in succession. The first part of the charge is ignited by a low power ignition device.
However, this ammunition is complex because it requires the assembling of several finely engineered parts. Additionally the transition between combustion of the first charge and that of the second charge is difficult to control, which means there is the risk of reducing the output of the propulsive charge and therefore the performance of the ammunition.
An ignition device comprising fuses which traverse the propulsive charge is known from document EP-0 344 098. This design, developed for large calibre ammunition is, however, complicated to use.